What was found
DOC HOWARD MACH II STC SYSTEM. AFTER A SCHEDULED 300 HOUR INSPECTION, AIRCRAFT WAS TEST FLOWN, FINDING AOA SYSTEM INOPERATIVE. SYSTEM WAS TROUBLESHOT, FOUND TO BE SATISFACTORY ON GROUND. IN FLIGHT AOA REMAIN STEADY, NO STALL WARNING, PUSH/PULLER FUNCTIONING WHILE EXPERIENCING WING AND TAIL BUFFET. SAFETY RECOMMENDATION INITIATED.